The Rod of Asclepius, left, with a single snake, is the symbol of medicine. Unfortunately, a large number of commercial American medical organizations instead use the caduceus, right, which has two snakes. Asclepius was the Greek god of healing, but the caduceus was wielded by Hermes and connotes commerce, negotiation, and trickery.

The confusion began when the American military began using the caduceus in the late 19th century, and it persists today. In a survey of 242 healthcare logos (reported in his 1992 book The Golden Wand of Medicine), Walter Friedlander found that 62 percent of professional associations used the rod of Asclepius, while 76 percent of commercial organizations used the caduceus.

“If it’s got wings on it, it’s not really the symbol of medicine,” the communications director of the Minnesota Medical Association told author Robert Taylor. “Some may find it hard to believe, but it’s true. It’s something like using the logo for the National Rifle Association when referring to the Audubon Society.”